This is great! I would hang out in the arena spamming my First Aid, and enjoy a couple fights when others come hoping to get my defensive abilities up quicker.
... for abilities just to level faster when in the arena (say 2x)
If abilities leveled faster in the arena it would be positive reinforcement.
No one is a looser since abilities are leveling faster.
As for something else, put a Summer Green Wyvrn in there with a completely random spawn timer. ie., it could spawn within 3 minutes of the last, or it could spawn 4 hours after the last. That way no one can time it, and only those there when it pops have a chance at it.